Modern mobile computing systems such as personal computer notebooks and hand-held e-mail retrieval devices are being provided with increasing functionality and performance. Most personal computer notebooks are being shipped with built in wireless data networking capabilities, as well as relatively large display screens, increased storage, and greater processor performance. In addition, in roads have been made into improving battery life by a combination of power consumption reduction techniques and rechargeable batteries having greater energy density.
Nevertheless, mobile systems are still restricted by their relatively high power requirements. Their batteries often need to be recharged, typically by plugging into an AC wall outlet. Despite the advances in power management and battery technology, most notebooks under typical usage have a battery life of no more than three or four hours. In the case of an all day meeting however, a fully charged, spare battery pack will be necessary to power the system for the duration of the meeting. As an alternative, the system must be plugged into a wall outlet via its corresponding AC adapter and power cable. Thus, with most modern notebooks, the user will need to bring either the AC adapter or a charged, spare battery, else he may need to use the system very conservatively to preserve battery life.
In another field, a modern computing system (be it for example a server or a desktop personal computer) has a network interface that allows a host processor in the system or machine to communicate with other nodes as part of a computer network. The network interface includes a network controller integrated circuit device that communicates, either via wireless connection or via a cable (such as an Ethernet cable) with the other nodes. Modern network interfaces are being enhanced with management capability. The management capability allows the interface, in concert with a remote node, to be used to discover, heal and protect the system, even while the system is powered off. For example, there is the capability to monitor environmental sensors in the machine, and signal an alert to a remote node if for example a component of the machine is overheating. The network management capability may also include wake-up filters that monitor incoming packets from the network and upon detecting certain predefined information in these packets alert the host processor. This allows the machine to enter a low power consumption mode (e.g., a sleep mode) while still being in touch with the network.
The network interface and the rest of the machine is typically powered by the machine's primary power supply circuits. In the event primary power is down, a backup source such as an uninterruptable power supply (UPS) used with desktop and sever computers, may automatically activate itself to supply the needed power. If the machine is a mobile system, however, powering the network interface with the AC adapter disconnected will eventually drain the mobile system's rechargeable battery.
More recently, Power Over Ethernet technology has emerged that allows computing appliances such as internet protocol (IP) telephones, wireless local area network (LAN) access points, and Web cameras to receive power as well as data, over existing LAN cabling. In a familiar example, conventional telephone sets are powered from the telephone exchange through the same twisted pair that carries voice. Now, Ethernet devices such as IP telephones and Web cameras can be powered over the same LAN cable through which they communicate. A UPS connected to an Ethernet switch or a Power Over Ethernet mid span hub (in a network equipment cabinet), helps guarantee power to the appliance, even during main power failure.